Production of photographic diazotype prints



Jan. 14, 1941. P; DIETERLE 2,228,562

PRODUCTION OFAPHOTOGRAPHIG DIAZOTYPE PRINTS Filed March 17, 1938 E mz3.

Ic7////// /V //fz2////A i INVENT'OR.

Y A z/elere gy# @x15 r2( ATTORNEYS UNITED. STATES PATENT OFFICE.

PRODUCTION or rHo'roGRArmo nmzorYrE rRIN'rs Paul Dieterle, Chicago, I ll., assigner to Eugene Dietzzen Co., Chicago, Ill., a corporation of ware Application March 17, 1938, Serial No. 196,462

8 Claims. (Cl. 95-6) The present invention relates to the productype used in the dry'development process, nametion of diazotype prints. f ly, one that has been treated so that it com- According to the diazotype printing or reproprises both vthe diazo compound and coupling duc'ing process, paper or any other suitable carcomponent. After exposure under a tracing, for

rier or suppont having thereon ya light-sensitive example, the powdered, non-volatile, alkaline 5 diazo compound is exposed to light under a drawsalt lis dusted or spread uniformly over the suring, tracing or other image so as to destroy or face thereof and the paper then placed in an decompose the diazo compound at the points to atmosphere containing steam or vapor. which the light penetrates, the portions of the It will be apparent to those skilled in the art,

10 paper overlaid by the opaque areas of the drawhowever, that this development process results 10 ing being protected from such decomposition. from` the direct contact of the particles of the The print is then developed by causing the unalkaline salt with the paper in the presence of decomposed diazo compound on the areas overthe moisture and that, accordingly, for the proclaid by the opaque portions of the tracing toess ,to work satisfactorily the alkaline salt must,

combine or couple with a coupling component therefore, be very evenly and finely distributed or diazo dyestuff component to produce a colored over the entire surface of the paper. This procimage corresponding to the original design. ess additionally requires a relatively long time Diazo compounds suitable for use in the diazofor development, is characterized by the necessity type process have in general the property of for apparatus maintaining atmospheres of steam chemically combining wyith so-called coupling or vapor. and may tend to cause the lines of the 20 components or diazo dyestuff components under final printing to bleed or spread. alkaline or relatively alkaline conditions. Ac- The present invention is related more specificorciingly, it is normally necessary for the procally to the so-called dry development process duction of a substantial dye formation at the and has for its object to overcome the disadvanareas corresponding to the image to be produced, tages of this process as well as the other hitherto 25 that development be carried out in alkaline practiced diazotype development processes and media or at least at a predetermined minimal to permit development by simple and' rapid steps pH corresponding to the lowest pH at which the without the necessity for complex equipment or coupling of the particular diazo compound and obnoxious atmospheres. According to the prescoupling component will take place. ent invention the development of the diazotype 30 Various processes have been proposed for deu prints is effected by subjecting paper containing veloping diazotype prints, among which is the the diazo compound and coupling component, semi-dry process wherein the paper exposed to after exposure to light under a design, to gases light under a tracing as above is subjected to given olf by the decomposition of ammonia comtreatment with an aqueous solution containing pounds under the influence 'of heat.A .5 an alkali and a coupling component. 'Ihe ammonia compounds which have been vAccording to the so-called dry process, on found particularly suitable for development of the other hand, the paper or other carrier or diazotype prints, in accordance with the present support having thereon both the diazo compoinvention, are the compounds of ammonia with 40 nent and the coupling component is, after exweak acids and it has been found that superior 40 posure as above, developed by subjecting the results are attained when employing compounds paper to an atmosphere containing ammonia of ammonia and carbonic acid, such as, for exvapor for a suflicient length of time to raise the ample, ammonium carbonate, ammonium bicarpH of the paper and the moisture content sufbonate, ammonium sesquicarbonate, which deciently to permit dye formation. The dry decompose freely at temperatures slightly elevated 45 velopment process is, rst of all, objectionable above room temperature with the production of due to the necessity for the use of obnoxious and free ammoniagas and water vapor. corrosive ammonia fumes. In addition, the de- Ammonium carbonate, for example, by Way of velopment by this method is normally relatively illustration, decomposes freely at temperatures in slow. the vicinity of 60 C. according to the following 50 It has further been proposed to develop diazoequation:l type prints by dusting the printwith a dry, nonvolatile, alkaline salt and applying moisture or (NH4)zcosHzo-)ZNHa-i'coz'zmo steam. More specifically, in accordance with Itis, therefore, only necessary to heat the solid thisprocess, there is employed a paper of the carbonates in juxtaposition to the exposed diazo- 55 type printing paper containing the diazo compound and the coupling component, to liberate the gaseous NH3 in contact with the exposed surface. Attention is particularly directed to the fact that, in order for development to take place, it is necessary for water in some physical form to be present in Contact with the paper. The necessary water Vapor is provided in the case of the ammonium carbonates by the decomposition thereof.

The invention is, however, not limited to the use of ammonium carbonates in view of the fact that numerous other ammonium salts are decomposable by heat with the liberation of alkaline vapors. Among these are the compounds of ammonia with weak acids such, for example, as ammonium acetate or formate although it is pertinent to point out that the compounds of this class do not possess all of the advantages of the preferred embodiment of the present invention and require the application normally of a relatively higher temperature for a greater length of time in order to result in development of the prints.

There are also other ammonium compounds besides the carbonates which decompose with the desired rapidity at only moderately elevated tem- .peratures. In this class are such compounds as ammonium amino sulphite and ammonium imino sulphite. Such compounds have the following probable structural formula (Chemiker Kalender, 1922, vol. I, by Biedermann) Ammonium amino sulte-NH2.SOz.NH4(P.20) Ammonium imino suliite-NH SO2.NH4)2(P 22 One method of procedure in developing diazotype prints in accordance with the present invention is illustrated more or less diagrammatcally in the drawing wherein:

Figure 1 is ,a perspective view of a diazotype printing paper which has been exposed, and a sheet of textile fabric having thereon a decomposable ammonium salt for development of the print.

Figure 2 is a perspective view showing the exposed diazotype layer overlaid with the layer of textile fabric and the developing salt and positioned in a heating element prior to development of Ithe print. y

Figure 3 is a detail elevational view taken at any point through the assembly shown in Figure 2 and illustrating more or less diagrammatically the mechanism of development.

Figure 4 is a perspective View of an exposed diazotype printing paper with the developing salt applied directly to the surface thereof.

Figure 5 is a view the same as Figure 2, but showing the arrangement of the diazotype printing paper and developing salt in the heating unit.

Figure 6 is a sectional elevation taken at any point through the assembly shown in Figure 5.

Reference is made more specifically to Figure 1 of the drawing, wherein `Ill indicates a sheet of paper comprising a light-sensitive diazo salt and a coupling component, the paper having been previously exposed to light under a tracing, as hereinbefore described. A generally coextensive sheet of a woven textile material is indicated at I2, of which widely varying types have been found useful. For example, the sheet. I2 may comprise a layer of cheesecloth', toweling or any other permeable inert fabric.

. The numeral I 4 generally refers to a heater of the hot plate type comprising a lower base I6 having an upper flat supporting surface, the base being hinged as at I8 to the upper plate 20. In the embodiment shown, the upper plate is provided interiorly thereof with a heating element 22 supplied with electricity from an electrical conduit 24 for bringing the upper plate to any predetermined temperature.

The exposed diazotype printing paper I0 is placed upon the upper surface of the plate I6 and overlaid with the sheet of textile fabric I2, the upper surface of which has been sprinkled, dusted, coated or otherwise provided with a decomposable powdered ammonia salt 26. The top plate 20, after being brought to a predetermined temperature, is pivoted downwardly about the hinge I8 until it resides flatwise upon the upper surface of the layer of textile material I2.

Assuming that the temperature of the heating unit is sufficient to decompose the ammonia salt, the action thereof will be equivalent to that illustrated more or less diagrammatically in Figure 3. Each particle of `the ammonia salt, upon being brought to the temperature sufficient to cause its decomposition. immediately liberates ammonia gas which permeates the interstices of the fabric or cloth I2, Attention is particularly directed to the series of arcuate dotted lines A in this figure, which illustrate the path of permeatlon or propagation of this ammonia gas; if the center of each of the arcs may be represented by the letter B, it will be seen that the gaseous decomposition prod"- ucts thereof will tend to propagate themselves in all directions. Since each of the plurality of small particles of salt .acts in the same manner, it is thought that it will be apparent that the surface of the diazotype printing paper I0 will be subjected substantially uniformly to the liberated gas.

Attention is further called to this fact by way of comparison to the hitherto known processes of development by means of non-volatile alkaline salts wherein the developing action is local with respect to each particle of salt. After the paper I0 has been exposed to these gases and vapors a sufcient length of time to expose the dye image, it may be removed from the heater and separated from the sheet of textile material I2.

The modified alternative form of procedure shown in Figures 4 to 6 comprehends the omission of the sheet of textile fabric I2. According to this procedure the exposed diazotype paper In is overlaid directly with a layer of the powdered ammonia salt 26 and placed in the heater I4 as before until the print is developed.

It has been found that superior results are obtained when proceeding in accordance with the first described preferred process wherein the layer of permeable fabric is positioned between the solid ammonia salt and the paper to be developed, and it is conceived that this result is due to the effect of the textile material in permitting a uniform concentration of developing vapors to contact the paper, as hereinbefore described.

The following is one specific example of a method of proceeding in accordance with the present invention, Diazotype printing paper, which has been coated with a solution formed by adding 2O parts by weight of the anhydride of chlorinated l-diazo, 2-oxynaphthalene, 4-sulphonic acid, and l0 parts by weight of resorcinol in 700 parts of water, to ay solution of 60 parts by weight of manganese chloride in 300 parts of water, and drying, is exposed to light under a tracing or other image to decompose the diazi compound on the portions of the paper unprotected from the light.

Dry ammonium carbonate in powdered form wise within the acid range'.

( (NH4)2CO3) is dusted on the surface of a sheet cf cotton cloth andthe cotton cloth is placed flatwise over the surface of the exposed dlazotype printing paper with the ammonium carbonate on top. The assembled sheets are then placed in a heating device, as shown in Figure 2, -the hot plate of which has a temperature of about-60 C., the dusted surface of the cotton cloth being indirect contact with the heated plate 20. The image on the paper is developed almost immediately, after which the plate may be raised and the developed paper withdrawn from the heater.

It is important to note that, while rapid and improved results are attained at the particular temperatures indicated, these may be varied Within wide limits. On the other hand, it will be preferred to maintain the temperatures below that elevated value suflicient to damage the paper y or other carrier for the print. Development may generally take place within any temperature range at-which the aforementioned decomposition of the salts occurs. It has been found preferable, When proceeding in accordance with the above specific illustrative embodiment, to employ temperatures above 7 C., although if less rapid developmentl is immaterial, lower temperatures are suitable.

According to another modified method of proceeding in accordance with the' present invention, the exposed diazotype printing paper is placed in contact with the sheet of textile material having thereon the layer of ammonium salt and the assembly is placed in a confined space at ordinary room temperature. After a period of time it will be found that development of the print has taken place. The same remarks obtain in regard to the other ammonium salts although it will be apparent that those which decompose at relatively elevated temperatures demand heating to a much higher range to effect development of the print. It is particularly important to note that, in accordance with the present invention, salts such as ammonium chloride may be employed and will produce satisfactory development of the diazotype prints even though they are not alkaline in character and in all probability produce decomposition to produce vapors or gases which are like- It is thought that this result may be attributed to the relatively superior penetrating power of alkaline substances in general which permits the liberated free ammonia gas to come in contact with and cause reaction of the diazo compound and coupling component before the hydrochloric acid gas. It is to be understood, of course, that this is merely a statement of theory and is not intended in any way to limit the scope of the disclosure.

The present invention provides a simple and effective method for developing diazotype prints in the dry form, which method is both clean and odorless. It will be understood from this disclosure that the heating units or the portions heated will be free from any deposition of solids in view of the fact that the'salt used is preferably completely volatile at the temperatures employed.

Moreover, since the decomposition reactions are in general reversible, the decomposition products normally rccomhine to form the original ammonia salt as soon as they reach the limits of the, heated zone, the ambient temperature of which is kept within the decomposition range, and, accordingly the process is odorless. All the inconvenience due to the handling of ammonia vapors is, therefore, avoided.

It is to be furtherunderstood that, while the present invention is particularly adaptable to development of diazo compounds and coupling com- I ponents which couple in the alkaline range, nevertheless the principles thereof are also applicable to development wherein the dye formation occurs atan acid pH. In carrying out this process, the diazo compound and the coupling component will be employed in conjunction with a carrier which is maintained normally at a pH sufficiently low to prevent coupling, the contact of the vapors from the decomposition of the ammonia salt performing the function of raising the pH into the range suflicient to permit coupling.

Aspointed out above in general, the decomposition products of the ammonia salts employed contain water vapor. In the case of ammonia salts which do not liberate moisture upon decomposition, it is comprehended that an atmosphere of moisture be provided in any suitable manner, such, for example, as by the auxiliary 20 formation of moist vapors from a body of water, or the addition of hydrated salts, for example, which have the property of supplying moisture at the temperatures employed. According to one specific method of proceeding when using am- 25 monia salts of this class, the layer of textile fabric l2 may be slightly moistened with water before use, or alternatively, a second dampened cloth may be placed thereover before subjection before development of the print, it is possible,

Within the scope of the present invention, to use a mixture, for example, of ammonium chloride and soda ash (NazCOa). These two salts may be mixed in dry powdered form and placed in contact with the layer of textile fabric which 40 voverlays the exposed printing paper, as hereinbefore described. When subjected to a temperature in the neighborhood of 60 C., for example, through the agency of the heating device shown,

these substances will first react with the formation of ammonium carbonate ((NH4) 2G03) which will immediately decompose through the inuence of the heat, with the liberation of concentrated ammonia gas in the vicinity of the paper.

It will be apparent that the source of the heating employed in the development process is entirely immaterial as long as the decomposable ammonia salt is subjected to the desired temperature for the liberation of free gaseous ammonia. The heating device may derive its energy,

not only from electrical heating units, but from steam or the combustion of fuels, or from any other source.

While they invention has been specifically illustrated in connection with printing papers it is l not so limited since the diazotype prints may be developed upon textiles, cloth, films or supports of various kinds hereinbefore included within the term carriersff By the term gases is intended to include all the non-solid expansible products of decomposition, including vapors and the like.

It is believed that various modifications and variations of the process coming Within. the scope of the following claims will be apparent ln accordance with the above disclosure. 7D

In accordance with the present disclosure it will be understood that by the term juxtaposition as used in the present specification and claims it is intended to cover the adjacent positioning of the dissociable substance and the paper to be developed preferably with a space therebetween, since, as pointed out above, the spacing of the solid reagent and the surface of the paper tends to result in a more uniform contact between the vaporous alkaline products and the paper. So also, in accordance with the present specification, the' term reversibly dissociable as applied to the reagents employed is intended to cover substances which, while not appreciably or substantially dissociable at ordinary temperatures, tend to dissociate rapidly and substantially at elevated temperatures to liberate the vaporous alkaline products and in particular those substances having dissociation products' which on lowering of the temperature tend to reassociate to form the original dissociable compound. That is to say, the present invention, in its preferred embodiment, comprehends not the use of substances which merely decompose to liberate ammonia with the creation of oi'ensive atmospheric conditions, but those reagents which, being reversible, permit the volatile ammonia or ammonia derivatives to recombine entirely or in part to obviate the conventional difficulties.

The invention is hereby claimed as follows:

1. The ymethod of producing photographic diazotype prints which comprises subjecting the surface of a carrier having thereon a dry, lightsensitive diazo compound and a coupling component to exposure to light under a design, overlaying the so exposed carrier with a permeable layer of material carrying on the outer portions thereof a decomposable ammonia compound, and subjecting the assembly to an elevated temperature of suiicient magnitude and for a suiiicient length of time to liberate ammonia by decomposition of said compound whereby to rapidly develop the print. 2. The method of producing photographic diazotype prints which comprises subjecting a carrier having thereon a substantially dry, lightsensitive diazo compound and a coupling component to exposure to light under a design, overlaying the carrier with a sheet of textile material, carrying on the outer surface thereof an ammonia salt freely decomposable at an elevated temperature, and subjecting the assembly to said elevated temperature for a sullcient length of time to liberate ammonia in Contact with said carrier whereby to develop the print.

3. The method of producing photographic diazotype prints which comprises providing a carrier having thereon a light-sensitive diazo compound and a coupling component, exposing said carrier to light under a design to decompose the diazo compound on the portions thereof which are not protected from the light, applying a quantity of a dissociable ammonia compound to one side of a layer of permeable, inert sheet material, placing said layer of sheet material over the exposed surface of the carrier With said one side away from said carrier, and subjecting the assembly to a temperature sufficient to substantially decompose the salt, with the liberation -of a substantial proportion of alkaline vapor adjacent the surface of the carrier whereby to rapidly develop the print.

4. The method of producing photographic diaz'- otype prints which comprises providing a carrier having4 associated therewith a light-sensitive diazo compound and a coupling component, subjecting said carrier to exposure to light under a design, applying to the surface of said exposed carrier a sheet of textile fabric having on the outer surface thereof a substantially dry, particulate ammonium carbonate compound, and subjecting the assembly to an elevated temperature sufficient to substantially decompose the ammonium carbonate compound and to liberate the vaporous decomposition products thereof adjacent the surface of said carrier whereby to substantially instantaneously develop the print.

5. In a diazotype developing device of the class described, a permeable web having retained thereon a dissociable ammonia salt,heating means having a portion thereof adapted tol be locally heated to an elevated temperature above normal and being formed to accommodate said Web, said heating means providing a space to accommodate a diazotype printing carrier in adjacent relationship to the web while subjecting the surface at least of said carrier to said predetermined elevated temperature for causing dissociation of the ammonia salt with the development of the print.

6. In a diazotype developing device of the class described, a permeable web having on its upper surface a reagent capable of reversibly dissociating at an elevated temperature above normal to form an alkaline vapor, and heating means having a portion thereof adapted to be locally heated to an elevated temperature above normal and being formed to accommodate said web, said heating means providing a space to accommodate a diazotype printing carrier below and adjacent the web while subjecting the surface at least of said carrier to said predetermined elevated temperature for causing dissociation of the ammonia salt with the development of the print under the influence of the alkaline vapor liberated.

7. A developing device for the development of diazotype prints employing diazotype paper having a diazonium component and a coupling cornponent thereon and comprising a permeable web of material having thereon a reversibly dissociable reagent adapted to dissociate at a predetermined elevated temperature with the liberation of an alkaline vapor, heating means having a predetermined zone adapted to maintain said elevated temperature and adapted to accommodate said web within said zone, said zone being formed to accommodate a portion at least of a diazotype carrier in juxtaposition to the web whereby to permit development of the print by the liberated alkaline vapors.

8. A dry method for developing diazotype prints comprising arranging a diazotype printing carrier in the vicinity of a reversibly dissociable compound which is an ammonia derivative and which is adapted to reversibly dissociate under the iniluence of an elevated temperature above normal to liberate alkaline vapors, arranging a permeable web between said reversibly dissociable compound and the printing carrier to be developed whereby to uniformly distribute against the carrier Vaporous products liberated by the said dissociable reagent and subjecting said assambly to said predetermined elevated temperature at a localized zone to cause dissociation with the development of the print. 5 PAUL DIETERLE. 

